Gasoline or diesel. In some rare engines ethanol is burned, of a mixture of gasoline and ethanol.
Coming up with this answer would've been easier than posting this question here.
If this is for your homework, then try actually using your brain, that's what this is about. Not wether you finished it or not.
In an internal combustion engine, the provided energy is chemical energy. By means of combustion it is transformed into heat energy. This heat energy is transformed in to motion/kinetic energy in an internal combustion engine.
In an internal combustion engine fuel is burned in a combustion chamber or cylinder inside the engine
combustion
Thermal Energy
Thermal Energy
An internal combustion engine converts chemical energy into Thermal Energy, and converts thermal energy into mechanical energy via the pistons, connecting rods, and crankshaft .
to produce mechanical energy
a gasoline engine is an Internal combustion engine
The internal combustion engine is used in almost everything that needs power or motive traction. Cars, trucks, motorcycles, boats, ships, aircraft, and many other things use internal combustion engines. The internal combustion engine is needed to convert fuel chemical energy to rotational mechanical energy, which can now be used for many different applications.
burning fuel
An external combustion engine is where something is burning outside of the actual engine and the energy is transmitted to the engine via something. (e.g. boiler creates steam that goes to the engine a.k.a. steam engine) In an internal combustion engine, the burning happens in the actual cylinders of the engine. (e.g. car engine)
Internal engine has its energy ignited in the cylinder. like 99.9% of engines today An external combustion example is a steam engine where the heating prosses is done in an boiler out side the engine.